There has been an explosion in demand for low-calorie and functional sweeteners capable of preventing excessive caloric intake, obesity and tooth decay owing to sugar consumption.
D-tagatose is an ideal low-calorie sweetener as an alternative sugar that can satisfy such consumer demand. D-tagatose has about 90% the sweetness of sucrose, thus being substantially identical thereto, but has 30% the calories of sucrose.
Further, it is known that D-tagatose, a stereoisomer of D-galactose, has low metabolic speed and absorption rate in the body, and thus can be used as a low-calorie sweetener without side effects (see: JECFA Sixty-third meeting, Geneva, 8-17 Jun. 2004—Food Additives).
Only 20% of D-tagatose is absorbed in the small intestine and the remaining 80% thereof is moved to the large intestine where intestinal microbes live and selectively accelerates the production of lactobacillus, thereby producing short chain fatty acids. Particularly, D-tagatose has a prebiotic characteristic of producing butyrate, which is known to help prevent colon cancer, in large quantities (up to 50% of the total short chain fatty acids). Further, D-tagatose is a natural sugar having a low-calorie value of 1.5 kcal/g and has attained GRAS (Generally Recognized As Safe) status under the U.S. Food and Drug Administration (FDA), thereby allowing use as a functional sweetener in foods, beverages, health foods, diet additives, and the like.
However, D-tagatose is not often found in nature and is a rare sugar present only in trace amounts in dairy products and some plants. In order to use D-tagatose as a low-calorie and functional sweetener, it is essential to develop a method for mass production of D-tagatose from inexpensive raw materials.
U.S. Pat. Nos. 5,002,612 and 5,078,796 disclose a method for producing D-tagatose by hydrolyzing lactose or lactose-containing materials by adding lactase to a mixture of D-galactose and D-glucose, removing optional D-glucose from the mixture, and then chemically isomerizing D-galactose into D-tagatose.
Thus, an essential intermediate in the enzymatic production of D-tagatose is D-galactose. Currently, supply of D-galactose developed up to now is restricted to hydrolysis of lactose
However, lactose prices vary due to unpredictable factors, such as amount of raw milk produced according to weather, demand for powder milk, changes in lactose consumption in third world countries, and the like, and exhibit a unique price pattern of repeating fall and rise in price. Such price fluctuations in the raw milk market make stable supply of raw materials for producing D-tagatose difficult.
According to the present invention, it is possible to obtain D-galactose from inexpensive whey permeate or dried whey permeate occurring in the process of producing whey protein isolates and to use D-galactose to produce D-tagatose. Therefore, stable supply of raw materials and price stabilization of D-tagatose can be ensured, thereby creating considerable added value.